1. This is actually a bad idea as the post exposes your supposedly secret post-to-blog email on your blog post. Pretty soon your blog will be spammed.
2. If that (secret email included in the post) gets fixed, you wouldn't have to add the blogger email to a circle. You just need to add it to your Google contacts list and name it as Post to Blog - [Name of Blog] or something just in case you forget the email address. You then share G+ posts to that email.
3. It would be good to share the post to the Public so they could add comments to the G+ post instead of the comments section of Blogger, which is experiencing a lot of problems right now. A ready link is provided, so no worries.
4. But if you share with the Public, then you might have to add the secret blogger email into a circle so you could change the notification settings. Otherwise, your blog would be spammed with comment notifications.